アナモックス反応による化学工場排水中の窒素処理実証

摘要

Pilot-scale tests were carried out for nitrogen removal from ammonium plant effluent using gel carriers on which anaerobic ammonium oxidation (anammox) sludge was immobilized. The nitrogen removal system was equipped with an anammox vessel of 5 m~3 volume and the pretreatment processes were carried out for continuous feeding tests. The nitrogen removal in the anammox vessel could be started up within approximately 2 months of acclimation using ammonia synthetic plant effluent (ammonia wastewater) at 30℃. After that, stable nitrogen removal in the anammox vessel was confirmed at 16.1℃ even though the influent was changed to another kind of wastewater based on urea. Moreover, nitrogen removal in the anammox vessel reached the designated denitrification rate within 3 days at 30℃ after influent wastewater was returned to the original ammonia wastewater. Finally, the anammox vessel was operated using the ammonia wastewater at a low water temperature. The nitrogen conversion rate was stably observed 1.9 kg-N·m~3·d~(-1) at 17.1℃. These results strongly suggest that this nitrogen removal system using anammox gel carrier can be applied to nitrogen removal from industrial effluent under low water temperature.%包括固定化したアナモックス担体と反応槽容積5m~3規模のアナモックス槽を用い，前処理プロセスと組み合わせ，化学工場排水中の窒素除去の実証試験を行った。高水温のアンモニア製造排水を用いて，水温30℃条件で処理性能の立上げを行った結果，アナモッタス槽は約2ヶ月で所定の処理性能を得た。その後，排水が低水温の尿素排水に変更され，水温16.1℃でアナモッタス槽を運転した結果，安定した処理性能を得た。再度，アンモニア製造排水に切替わり，水温を約30℃に上昇させたが，アナモックス槽は3日以内で所定の窒素除去速度まで上昇した。次に，水温17.1℃の低水温条件下で運転した結果，安定して窒素除去速度1.9kg-N·m~3·d~(-1)を得た。包括固定化アナモックス担体を用いた本システムは，産業排水処理で求められる大幅な水温変動や排水種類の変動に対応でき，さらに低水温条件下においても適用できることを実証した。